Apparatus for storing and exposing a radioactive source

ABSTRACT

A source exposing head adapted to be mounted on a container of radiation resistant material which has a passageway within which a movable radioactive source is stored. The head is a mass of radiation resistant material providing a shielded extension of the passageway of the storage container and provides an annularly shaped source exposure aperture externally of the storage container.

Forrer Assignee:

APPARATUS FOR STORING AND EXPOSING A RADIOACTIVE SOURCE lnventor: Gilbert R. Forrer, Barberton, Ohio The Babcock & Wilcox Company, New York, NY.

Mar. 24, 1969 Filed:

Appl. No.:

US. Cl ..250/106 S, 250/108 R Int. Cl. ..G21f 5/02 Field of Search ..250/106, 106 S, 108

References Cited UNITED STATES PATENTS Sauerwein et a1 ..250/ 106 [451 Apr. 11, 1972 Primary Examiner-James W. Lawrence Assistant Examiner-Davis L. Willis Att0mey--Joseph M. Maguire [57] ABSTRACT 10 Claims, 8 Drawing Figures I L I Patented April 11, 1972 2 Sheets-Sheet l INVENTOR. Gilberf R. Forrer ATTORNEY 2 Sheets-Sheet 2 Patented April 11, 1972 APPARATUS FOR STORING AND EXPOSING A RADIOACTIVE SOURCE BACKGROUND AND SUMMARY OF THE INVENTION Devices employing radioactive substances as sources of penetrating radiation for non-destructively determining the structure of metal workpieces are well known in the art. A photographic image of the structure of a given metal workpiece may be formed on a radiation sensitive material mounted on one side of the workpiece, by exposing the opposite side of the workpiece to emissions from a suitably shielded source. The image, or radiograph, is formed as a result of differential absorption of radiation by the workpiece. Since the exposure effects of radioactivity on humans are cumulative, it is an industry wide practice to attempt to build safeguards into devices which carry radioactive substances to protect personnel from being accidently exposed to even minor dosages of radioactivity over prolonged periods of time. In addition, individual radiographs should be obtained as rapidly as possible to minimize the time interval within which a person could be inadvertently exposed. The present invention was conceived with these factors in mind and generally comprises a source exposing head provided with a supplementary source moving member and may be used, for example for radiographically examining cylindrically shaped workpieces such as industrial pressure vessels, tanks and the like.

In many prior art devices the source of radio activity is moved between an unexposed position within a passageway formed in a container of radiation resistant material commonly, referred to as a coffin; and an exposed position, within or externally of the passageway, by means of a wire connected to the source. If the wire is inadvertently separated from the source and the source exposed, it is highly hazardous for personnel to approach the coffin to attempt to shield the source by returning it into the coffin. To obviate this problem, a source exposing head as herein described may be mounted on most commercially available coffins to provide a supplementary source moving member. The source moving member is arranged for pushing rather than pulling the source from its exposed to unexposed position in the event that the wire is separated from the source. It is an additional feature of the invention to provide such a head with an annularly shaped source exposing aperture for simultaneously exposing a full 360 section of a cylindrically shaped workpiece to radiation, to allow, for example, for rapidly radiographing an entire circumferential weld seam of a pressure vessel.

As will hereinafter be more fully described, the invention is an improvement in combination with a coffin having a passageway within which a movable radioactive source is stored such that it may be moved between a position within the coffin and a position externally of the coffin, and means for so moving the source; the improvement being a source exposing head comprising an elongated annular member, a radiation resistant material encircling at least a portion of the longitudinal length of the member; the radiation resistant material forming a source exposure aperture to allow radioactive emissions from the source to emanate laterally, preferably radially, of the longitudinal length of the member when the source is moved extemallyof the coffin to a position within the member; and an elongated body of radiation resistant material slidably movable within the member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a elevation view, partly in section, of a coffin provided with an embodiment of a source exposing head.

FIG. 2 is a elevation view of an embodiment of the source exposing head.

FIG. 3 is an end view of the head shown in FIG. 2.

FIG. 4 is a compound view of the head of FIG. 2 taken substantially along the line 4-4 of FIG. 2.

FIG. 5 is a elevation view, partly in section, of the preferred embodiment of the source exposing head.

FIG. 5A is a partial sectional elevation view of an enlarged portion of the head of FIG. 5 taken along the line 5-5 of FIG.

' FIG. 6 is an end view ofthe head ofFIG. 5.

FIG. 7 is a reduced sectional view of the head of FIG. 5 taken substantially along the line 7-7 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing wherein like reference numerals designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a source exposing head 10 adapted to be mounted on a coffin 12 of the type comprising a body of radiation resistant material 14, enclosed in a rigid shell 16, and having a bent passageway 18 formed therein to receive a radioactive source 20 of penetrative radiation which is attached to wire 22 so it may be moved and positioned within the passageway by endwise moving the flexible wire 22 connected to the source and extending externally of the cofl'm 12.

The coffin shown is intended to be representative of any commercially available device within which a movable radioactive source stored in a passageway 18 is susceptible to movement between a position within the device to a position externally thereof. These positions are usually the shielded and unshielded positions of the source and the source is movable between the positions by moving a wire or cable or the like which is connected to the source for that purpose. For example, the cable moving means 13, of FIG. 1, is intended to be representative of means well known in the art for imparting the desired motion to a wire or cable or the like.

Assuming the head 10 is not connected to the coffin 12, the shielded position is ordinarily a point such as the one designated by the numeral 24 or the like, a point. located within the passageway where the source is completely shielded by a material able to block the passage of radioactive emissions from the source. On the other hand, the unshielded position is ordinarily a point such as the one designated by numeral 26 or the like, a point located within or near one end of the passageway where the source emanations are not completely blocked.

In the coffin shown in FIG. 1, the end of the passageway 18 is flared outwardly to form a cone-shaped exposure aperture 27 at the surface of the coffin. If the head is not mounted on the coffin the source could be moved to position 26 to expose an object externally of the coffin. However, with the head connected to the coffin, the unshielded position 26 becomes shielded, the exposure aperture 27 of the coffin being covered with the head, and the source must now be moved to a position externally of the coffin to another unshielded position to expose an object to radiation. The source exposing head described herein effectively shields the source externally of the coffin and provides an exposure aperture for exposing objects externally of the coffin to radiation from the source.

An embodiment of the source exposing head 10 for radiographically examining a circumferentially extending weld seam joining abutted sections of a cylindrically shaped metal workpiece is shown in FIGS. 2-4. The head basically comprises an axially elongated annular member 30, a mass of radiation resistant material 32 encircling at least a portion of the longitudinal length of the member 30 to form an annularly shaped source exposure aperture 35, and an elongated body 36 of radiation resistant material which is endwise slidably movable within the member 30. The source exposure aperture 35 allows radioactive emissions from the source to emanate laterally of the longitudinal length of the member 30 when the source is moved externally of the coffin to a predetermined position within the member.

As hereinbefore indicated, the head is adapted to be mounted on a coffin 12. In the embodiment shown in FIGS. 2-4, the mounting means comprises a plurality of L-shaped members 38, each of which has one leg connected to the head and the other leg extending outwardly of the head for connection to the coffin by means well known in the art. The mounting means preferably includes a forward portion 34 of the annular member 30, formed to extend from the shield for insertion into the passageway 18 of a coffin 12. In practice, the radiation resistant material 32, or shield, is a mass of lead at least partially enclosed in a casing 31 of sheet metal such as stainless steel or other structural sheet material well known in the art.

When the head is mounted on the coffin as shown in FIG. 1, the passageway of the coffin is in open communication with the interior of the annular member 30 thus in effect extending the coffin passageway. Similarly, the shield 32 acts as an extension to the penetration resistant material 14 of the coffin, Thus the position 26 to which the radioactive source is ordinarily moved to expose an object located externally of the coffin is no longer available for that purpose. The source must now be moved to exposure position 26A (FIG. 4) since the exposure aperture 35 is now defined by the source exposing head 10. Since the exposure aperture 35 of the head has a different configuration than the exposure aperture 27 of the coffin; the head may be considered to be an auxiliary exposure aperture forming device adapted to be mounted on a coffin, a device providing a differently configured exposure aperture than the one which is provided with the coffin.

The annular member 30 is preferably an open-ended tubular member of stainless steel encircled with penetration resistant material throughout its longitudinal length except at one of its end portions, the forward portion 34; and throughout a narrow portion 37 of its length. The narrow portion 37 is located approximately centrally of the length of the annular member where the annulus defines a narrow annularly shaped window, or base, through which radiation from the source may enter into the exposure aperture 35. The aperture 35 is of approximately wedge-shaped cross-section, flaring outwardly from its base to allow a diverging annularly shaped beam of the radioactive emissions to emanate from the head, radially of the annular member, when a source is moved to position 26A within the member. Emissions are prevented from emanating from the rearward end 42 of the member 30 by the elongated body 36.

The body 36 is a circularly shaped rod comprising a metal tube 36A that is at least partially filled with a radiation resistant material 36B. The tube 36A is slip-fitted with the annular member so that it is endwise slidable within the annulus. The tube is preferably made of stainless steel. As shown in FIG. 2, the rod 36 is provided with a pair of recesses 33, formed inwardly of its longitudinally extending outer surface, and a male lug which extends outwardly of the surface near the rearward end 42 of the rod. The recesses are spaced apart from one another along the longitudinal length of the rod and aligned with the lug 40.

A spring loaded detent 44, mounted on the casing 31 of the shield 32 via a U-shaped supporting bracket 46, is provided to engage one or the other of the recesses 33, depending on the position of the rod 36 within the annular member. When the rod is moved outwardly of the member 30, toward the rearward end 43 of the member as shown in FIG. 2 and 4, the end of the detent nearest the rod is spring loaded into engagement with recess 33A, the recess nearest the forward end 47 of the rod; whereas if the rod were moved sufficiently inwardly of the annular member toward the forward portion 32 of the member, the same end of the detent would be spring loaded into the recess 333, the recess nearest the rearward end 42 of the rod. The spring associated with the detent 44, is seated within the U-shaped bracket 46 on one of the outstanding bracket legs to axially receive the detent as it is passed through opposing openings formed in each of the bracket legs. A female lug 41, connected to the detent by means well known in the art, is carried toward the rod as the spring expands to carry the detent into engagement with the recesses. The female lug also acts as a mating member for the male lug. The spring may be compressed to withdraw the detent from either of the recesses and allow the rod to be moved toward either end of the member 30. When the rod is moved inwardly toward the forward end of the member, the free end of the male lug projects through a slot 45 (FIG. 4) fonned in the female lug 41. In this position, an opening, or hole 49, which is formed in the male lug 40 and sized to receive a padlock or other safety locking means, may be provided with a lock to positively prevent the rod from being inadvertently withdrawn outwardly of the annular member by unauthorized personnel.

Of course, it is well within the scope of the invention to connect the end of the spring nearest the rod 36, directly to the detent 44 and pivot the female lug 41 to the detent. The malefemale lug and lock arrangement provides a secondary latching means for locking the rod in place within the member 30; the latching arrangement provided by the spring loaded detent cooperating with the recesses being the primary latching means for arresting motion of the rod.

The preferred embodiment of the invention is shown in FIGS. 5-7. As in the previously described embodiment, the head 10 is particularly adaptable to radiographically examining circumferentially extending weld seams and basically comprises an elongated annular member 30, which is lengthwise encircled with a mass 32 of radiation resistant material having an annularly shaped exposure aperture 35, and an elongated body 36 of radiation resistant material which is endwise slidably movable within the member 30. As with the previously described embodiment, the head further comprises primary and second latching means for arresting the motion of the rod 36.

Again, the mounting means is connected to the head and includes a forward portion 34 of the member 30 which extends from the shield for insertion into the coffin. However, instead of L-shaped members 38 of FIGS. 2, 3 and 4, the mounting means includes a flange 50 that extends laterally from the head and is adapted to be connected to the coffin by means well known in the art.

The member 30 of the preferred embodiment principally differs from that of the embodiment shown in FIGS. 2-4 in that the approximately centrally located narrow portion 37 of its length, the portion within which the source is positioned for exposing objects externally of the head, is reduced in crosssection as compared to the cross-section of the member at either side of the central portion 37. At the same time, the end of the aperture farthest from the member is enclosed by an annularly shaped plate 52 which serves to strengthen the head structure and enclose the aperture. Thus the exposure apertures of both embodiments have the same form. They are annularly shaped apertures of approximately wedge-shaped cross-section flaring outwardly from their respective bases and the annular member. But the exposure aperture of the preferred embodiment is a hollow annular space within the casing 31 that encloses the radiation resistant material 32, since the plate 54 is connected to the casing 31 so as to form a part thereof.

As shown in FIGS. 5 and 6, the casing 31 is a cylindrically shaped shell of welded construction that encloses the member encircling a mass of radiation resistant material. One end of the casing 31 is formed by an end plate 52 which is provided with a centrally disposed opening aligned in registry with the member 30 to receive the rod 36. Again, the rod 36 is a circularly shaped rod comprising a metal tube 368 which is at least partially filled with radiation resistant material 36A, preferably lead. In practice, the longitudinal length of the radiation resistant material is approximately half that of the tube, and the tube 36B is of thicker cross-section throughout its lead-filled portion 37A than throughout its unfilled portion 478. As shown in 5A, the inner diameter of the tube 368 is relatively a constant throughout the length of the tube whereas the outer diameter is greater at the forward end portion 47A of the tube than at the rearward end portion 478. The outer diameter of the tube is reduced approximately midway along its length to form a fiat, laterally extending, surface or lip 47C in the tube. In practice, the centrally formed opening in the end plate 52, is a circular opening of lesser diameter than the inner diameter of the member 30. The forward end portion 47A is sized to slip fit within the member 30 and the rearward end portion 478 sized to pass through the end plate opening. Consequently, to mount the rod within the member 30 the rod 36 is passed rearward end first through the forward end of the member. The rod is rearwardly movable within the member until the lip 47C contacts the inner surface of the plate 52 which acts as a stop for the rod. It should be appreciated that with this arrangement, when the head is mounted on the coffin the rod cannot be accidently removed from the head. In effect, the lip and stop arrangement provide a tertiary means for arresting the motion of the rod within the annular member such that the head may be safely approached from its rearward end when the source is moved to position 26A within the member.

As with the previous embodiment, the rod is provided with a pair of recesses 33A and 33B, adapted to receive one end of a spring loaded detent 44 mounted on the head via a bracket 46. In this case the recesses are openings in the tube and the detent is a female U-shaped latch bolt bracketed to the end plate 52 and rotatable in place to mate with a male lug 40 extending outwardly from the end plate. With this arrangement, the primary and secondary latching means for arresting the motion of the rod are combined in a manner which allows the rod to be locked in place with a padlock or other locking means when the detent engages either of the recesses. In the previously described embodiment the rod can only be so locked in place when the rod is pushed forwardly within the annular member.

To add to the rigidity of construction of the head, the preferred embodiment is provided with a plurality of supporting members 60 which are preferably a series of struts mounted within the head and extending radially between the interior of the casing 31 and the exterior of the annular member.

With either embodiment it should be appreciated that if the source is moved to position 26A within the head and the cable connected to the source was then, through failure, separated from the source, or the source was otherwise unable to be returned to the coffin, the head could safely be approached from the rearward end of the rod, and the rod then physically rammed forwardly within the annular member to push the source back into the coffin. In addition, it should be appreciated that when the rod is moved into the forward end of the annular member the source cannot be positioned within the member without first moving the rod rearwardly. Thus the rod acts as a safety device for preventing the source from being accidentally exposed as well as a supplementary source moving member.

Further, as hereinbefore indicated, since the 360 exposure aperture of the preferred embodiment permits the circumferentially extending weld seams of cylindrically shaped workpieces to be rapidly radiographed the elapsed time within which personnel can possibly be exposed to radiation when radiographing such workpieces is reduced as compared to available prior art devices. This feature is thus an additional safety feature of the invention.

What is claimed is:

1. In combination with a coffin having a passageway within which a movable radioactive source is stored and means for moving the source between a position within the coffin and a position externally of the coffin, the improvement of a sourceexposing head adapted to be mounted on the coffin, the improvement comprising, a tubular member, a mass of radiation resistant material encircling a portion of the longitudinal length of the member and defining a source exposure aperture to allow radioactive emissions from the source to emanate laterally of the longitudinal length of the member when the source is moved laternally of the coffin to an exposed position within the member, and means supplementary to the source moving means for manually pushing the source from the exposed to an unexposed position including an elongated body of radiation resistant material slidably movable within the member and extending therefrom.

2. The combination according to claim 1 wherein the member is constructed and arranged to extend the coffin passageway externally of the coffin, and the source exposure aperture is an annularly shaped aperture.

3. The combination according to claim 1 wherein the elongated body is a rod comprising a tube containing radiation resistant material, and the rod is slip-fitted within the member.

4. The combination according to claim 1 wherein the aperture is an annularly shaped aperture permitting radiation from the source to emanate radially of a portion of the longitudinal length of the member for exposing an object externally of the head to radiation from the source.

5. The combination according to claim 1 wherein the head is provided with means for arresting motion of the rod within the member.

6. The combination according to claim 5 wherein the arresting means comprises primary and secondary means for arresting motion of the rod.

7. The combination according to claim 5 wherein the head includes a casing that encloses the mass of radiation resistant material, the rod has a recess formed therein, and the arresting means comprises a spring loaded detent connected to the easing to engage the recess.

8. The combination according to claim 5 wherein the head includes a casing that encloses the mass of radiation resistant material, and a first lug connected to the rod, and the arresting means comprises a second lug connected to the casing to engage the first lug.

9. The combination according to claim 7 wherein the head includes a first lug connected to the rod, and the arresting means further comprises a second lug connected to the casing to engage the first lug.

10. The combination according to claim 7 wherein the head includes a lug mounted on the casing, and the detent is a U- shaped latch bolt rotatable to mate with the lug. 

1. In combination with a coffin having a passageway within which a movable radioactive source is stored and means for moving the source between a position within the coffin and a position externally of the coffin, the improvement of a source-exposing head adapted to be mounted on the coffin, the improvement comprising, a tubular member, a mass of radiation resistant material encircling a portion of the longitudinal length of the member and defining a source exposure aperture to allow radioactive emissions from the source to emanate laterally of the longitudinal length of the member when the source is moved laternally of the coffin to an exposed position within the member, and means supplementary to the source moving means for manually pushing the source from the exposed to an unexposed position including an elongated body of radiation resistant material slidably movable within the member and extending therefrom.
 2. The combination according to claim 1 wherein the member is constructed and arranged to extend the coffin passageway externally of the coffin, and the source exposure aperture is an annularly shaped aperture.
 3. The combination according to claim 1 wherein the elongated body is a rod comprising a tube containing radiation resistant material, and the rod is slip-fitted within the member.
 4. The combination according to claim 1 wherein the aperture is an annularly shaped aperture permitting radiation from the source to emanate radially of a portion of the longitudinal length of the member for exposing an object externally of the head to radiation from the source.
 5. The combination according to claim 1 wherein the head is provided with means for arresting motion of the rod within the member.
 6. The combination according to claim 5 wherein the arresting means comprises primary and secondary means for arresting motion of the rod.
 7. The combination according to claim 5 wherein the head includes a casing that encloses the mass of radiation resistant material, the rod has a recess formed therein, and the arresting means comprises a spring loaded detent connected to the casing to engage the recess.
 8. The combination according to claim 5 wherein the head includes a casing that encloses the mass of radiation resistant material, and a first lug connected to the rod, and the arresting means comprises a second lug connected to the casing to engage the first lug.
 9. The combination according to claim 7 wherein the head includes a first lug connected to the rod, and the arresting means further comprises a second lug connected to the casing to engage the first lug.
 10. The combination according to claim 7 wherein the head includes a lug mounted on the casing, and the detent is a U-shaped latch bolt rotatable to mate with the lug. 